An edge detector detects a leading edge and/or side edges of a medium, such as a sheet of paper, foil, fabric or other sheet-like medium, while it is moving into and through a processing area of a media processing system. The media processing system can be, for example, a printer, a scanner or another device for processing sheet-like media. An edge detector can be used for detecting when a medium is entering the media processing device or a media processing zone and for monitoring skewness of the print medium while it travels through the media processing device.